Mice/Pregnant mice

QuestionHi I believe i have two pregnant mice. I had the male in with them for about two weeks before removing him and it has now been 38 days since I removed him and there is still no babies! But my females both look and act pregnant. They have been nesting for over a week and the one will always try to bite if I get to close. There bellies are pear shaped and ones is bulged more then the other. I think they are pregnant, but I just don't understand why they haven't given birth yet. Any suggestions?

AnswerHi Amanda,

If you were breeding them intentionally, it sounds like it is time to try again! As you probably know, the gestation period for mice is 21 days, give or take a couple. Even if they were late, if it has been 38 days since his removal, it sounds like the mating was unsuccessful.

There are some normal mousey behaviors that can appear like pregnancy ones, such as nesting. Mice naturally love to dig tunnels and arrange a nest or house in their home, so even though it may seem like they are preparing for new arrivals, they might just be getting cozy in their newly male-free home. Young mice that have just come home with you might also still have some weight to gain - a 2 month old mouse is certainly an adult, but will continue to grow and round out until 3 to 4 months, when the best breeding age begins. Lastly, this skittish behavior could also be a product of them getting used to you. If you have had them a long while, they might just be picking up on your excitement and getting nervous, but being with a male can be stressful to females even if for a short period.

For now I would work on getting them used to you so they don't get too anxious when they do successfully become pregnant. You were spot on with two weeks of being with the male, so I would just try it again, as it can take a few tries. If you still have no babies come along you might consider a new male, but I think he probably just needs another try.

Expertise

I can answer questions regarding mice as pets, mouse behavior, color and coat genetics, breeding techniques, and general health questions. I can help with caging and setup, nutrition, social issues, and what to do in most mouse emergencies (such as unplanned litters, injuries, fighting, etc.). I can also assist with questions pertaining to orphaned mouse pups, weaning litters, and questions of mating and birthing. I cannot answer questions about exotic or wild varieties of mice such as spiny or pygmy mice.
*****FOR EMERGENCIES, anything requiring immediate medical intervention, PLEASE take your mouse to a professional veterinarian or wildlife rehabilitator who works with mice as soon as possible!
IMPORTANT RESOURCES:
Raising Orphaned Mice: http://www.rmca.org/Articles/orphans.htm
Orphaned Mice Videos: http://www.youtube.com/user/CreekValleyCritters/videos?query=raising
Natasha's Your First Mouse: http://www.youtube.com/watch?v=RNK4uqNZTbA&feature=share
General Mouse Help: http://www.fancymice.info/
Mouse Info and Exotic Breeds: http://www.hiiret.fi/eng/species/

Experience

I have enjoyed the companionship of mice nonstop since 2004, and spent a year caring for them in a lab where I learned a great deal about their breeding, social needs, and health. I spent a few years breeding them, specifically working with albinos, marked mice, angora mice, and satins. My education never stopped - I am learning something new every day from current and well-established research thanks to the wonderful folks at the Jackson Laboratory, as well as from my wonderful mousey friends online. I also love learning from my terrific questioners here on AllExperts - you folks keep my passion for these amazing animals alive and well!

Education/CredentialsPartial University for a B.S. in Microbiology,
Partial University for a 2-year degree in Veterinary Technology (RVT cert),
C.E. classes in pathogens, aseptic technique, genetics, and applications